It is important to have insurance that covers you for the level of altitude that you will be trekking at. Many standard polices do not cover you for trekking to high altituides, such as on the Everest Base Camp Trek and Annapurna Circuit Trek which are over 5000m.
Below is a list of insurance companies that offer insurance for high altitude trekking.
For UK citizens
OTHER SUITABLE INSURANCE COMPANIES
Add the trekking up to 6000m option on recognised routes
For EU citizens only
The Extreme Adventure Pack covers trekking over 4,500m to any altitude (£750 access for air ambulance rescue in Nepal)
The SPORT EXTREME option covers you for trekking above 4000m
The SPORT PLUS option covers you for under trekking below 4000m.